Technical Field
The invention relates to a lens and a backlight module, and particularly relates to a lens capable of providing uniform light brightness and a backlight module.
Related Art
Generally, if light emitting diodes (LEDs) are disposed under a diffusion plate of a backlight module by a predetermined distance, an observer is liable to observe non-uniform brightness distribution on the diffusion plate. The predetermined distance is an optical distance (OD). Presently, the problem of non-uniform light brightness distribution may be resolved by increasing the optical distance or increasing a number of the LEDs to shorten a pitch between the LEDs. However, increase of the optical distance may increase a whole thickness of the backlight module, which is of no avail for a current trend of product thinness, and increase of the number of the LEDs may increase product cost, which is uneconomic. Moreover, a secondary optical lens may be configured to the LED to resolve the problem of non-uniform brightness distribution of the backlight module while the number of the LEDs is decreased or the optical distance is decreased. However, there is still a certain limitation of the optical distance in usage of the existing secondary optical lens, and the existing secondary optical lens may only be used in the optical distance of 25 mm. When the optical distance is decreased, referring to a schematic diagram of brightness distribution of a backlight module of FIG. 1, the existing secondary optical lens guides the light beam to an area A away from the LED C (having the secondary optical lens), such that the light beam around an area B close to the LED C (having the secondary optical lens) is inadequate to form a dark ring, by which another problem of non-uniform brightness is encountered.
Under the trend of product thinness, the current secondary optical lens may have the aforementioned problem of non-uniform brightness when the optical distance is decreased, so that the optical distance may not be effectively decreased. Therefore, how to reduce the optical distance while considering the brightness uniformity and product taste is an important issue to be developed.
U.S. Pat. No. 7,549,781B2 discloses an LED module including an LED chip, a chip substrate and a lens. U.S. Pat. No. 8,128,260B2 discloses a lens having a plurality of surfaces and refracting portions. U.S. Pat. No. 7,347,590B2 discloses a lens having a plurality of lens portions. U.S. Pat. No. 6,674,096B2 discloses a hemispherical transparent encapsulant of an LED package having a recess relative to an LED chip.
The information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not foam the prior art that is already known to a person of ordinary skill in the art. Further, the information disclosed in the Background section does not mean that one or more problems to be resolved by one or more embodiments of the invention was acknowledged by a person of ordinary skill in the art.